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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group JC. Zuniga 3 Internet-Draft B. Ponsard 4 Intended status: Informational SIGFOX 5 Expires: January 6, 2017 July 5, 2016 7 SIGFOX System Description 8 draft-zuniga-lpwan-sigfox-system-description-00 10 Abstract 12 This document presents an overview of the network architecture and 13 system characteristics of a typical SIGFOX Low Power Wide Area 14 Network (LPWAN), which is in line with the terminology and 15 specifications being defined by the ETSI ERM TG28 LTN group. It is 16 intended to be used as background information by the IETF LPWAN group 17 when defining system requirements of different LPWAN technologies 18 that are suitable to support common IP services. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on January 6, 2017. 37 Copyright Notice 39 Copyright (c) 2016 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. System Architecture . . . . . . . . . . . . . . . . . . . . . 3 57 4. Radio Spectrum . . . . . . . . . . . . . . . . . . . . . . . 5 58 5. Radio Protocol . . . . . . . . . . . . . . . . . . . . . . . 5 59 5.1. Uplink . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 5.1.1. Uplink Physical Layer . . . . . . . . . . . . . . . . 5 61 5.1.2. Uplink MAC Layer . . . . . . . . . . . . . . . . . . 6 62 5.2. Downlink . . . . . . . . . . . . . . . . . . . . . . . . 6 63 5.2.1. Downlink Physical Layer . . . . . . . . . . . . . . . 6 64 5.2.2. Downlink MAC Layer . . . . . . . . . . . . . . . . . 7 65 5.3. Synchronization between Uplink and Downlink . . . . . . . 7 66 6. ETSI LTN . . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 7. Network Deployment . . . . . . . . . . . . . . . . . . . . . 8 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 69 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 70 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 71 11. Informative References . . . . . . . . . . . . . . . . . . . 9 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 74 1. Introduction 76 This document presents an overview of the network architecture and 77 system characteristics of a typical SIGFOX LPWAN, which is in line 78 with the terminology and specifications being defined by the ETSI ERM 79 TG28 Low Throughput Networks (LTN) group [etsi_ltn]. It is intended 80 to be used as background information by the IETF LPWAN group when 81 defining system requirements of different LPWANs that are suitable to 82 support common IP services. 84 LPWAN technologies are a subset of IoT systems which specifically 85 enable long range data transport (e.g. distances up to 50 km in open 86 field), are capable to communicate with underground equipment, and 87 require minimal power consumption. Low throughput transmissions 88 combined with advanced signal processing techniques provide highly 89 effective protection against interference. 91 Because of these characteristics, LPWAN systems are particularly well 92 adapted for low throughput IoT traffic. SIGFOX LPWAN autonomous 93 battery-operated devices send only a few bytes per day, week or 94 month, allowing them to remain on a single battery for up to 10-15 95 years. 97 2. Terminology 99 The following terms used in this document are in accordance to the 100 ones defined by ETSI ERM TG28 Low Throughput Networks (LTN) 101 [etsi_ltn]: 103 Base Station (BS) - A Base Station is a radio hub of an LTN 104 system. 106 Device Application (DA) - An application running on the End Point 107 or device. 109 End Point (EP) - An End Point is a leaf node (aka device) of an 110 LTN system that communicates application data between the local 111 device application and the network application. 113 Low Throughput Networks (LTN) - Terminology used in ETSI to define 114 Low Power Wide Area (LPWA) networks. 116 Network Application (NA) - An application running in the network 117 at the opposite extreme of the device. 119 Registration Authority (RA) - The Registration Authority is a 120 central entity that contains all allocated and authorized End 121 Point IDs. 123 Service Center (SC) - Each LTN system has a single service centre. 124 The SC performs the following functions: 126 * EPs and BSs management 128 * EP authentication 130 * Application data packets forwarding 132 * Cooperative reception support 134 3. System Architecture 136 Figure 1 depicts the different elements of the system architecture: 138 +--+ 139 |EP| * +------+ 140 +--+ * | RA | 141 * +------+ 142 +--+ * | 143 |EP| * * * * | 144 +--+ * +----+ | 145 * | BS | \ +--------+ 146 +--+ * +----+ \ | | 147 DA -----|EP| * * * | SC |----- NA 148 +--+ * / | | 149 * +----+ / +--------+ 150 +--+ * | BS |/ 151 |EP| * * * * +----+ 152 +--+ * 153 * 154 +--+ * 155 |EP| * * 156 +--+ 158 Figure 1: ETSI LTN architecture 160 The architecture consists of a single core network, which allows 161 global connectivity with minimal impact on the end device and radio 162 access network. The core network elements are the Service Center 163 (SC) and the Registration Authority (RA). The SC is in charge of the 164 data connectivity between the Base Station (BS) and the Internet, as 165 well as the control and management of the BSs and End Points. The RA 166 is in charge of the End Point network access authorization. 168 The radio access network is comprised of several BSs connected 169 directly to the SC. Each BS performs complex L1/L2 functions, 170 leaving some L2 and L3 functionalities to the SC. 172 The devices or End Points (EPs) are the objects that communicate 173 application data between local device applications (DAs) and network 174 applications (NAs). 176 EPs (or devices) can be static or nomadic, as they associate with the 177 SC and they do not attach to a specific BS. Hence, they can 178 communicate with the SC through one or many BSs. 180 Due to constraints in the complexity of the EP, it is assumed that 181 EPs host only one or very few device applications, which communicate 182 to one single network application at a time. 184 4. Radio Spectrum 186 The radio interface is compliant with the following regulations: 188 Spectrum allocation in the USA [fcc_ref], 190 Spectrum allocation in Europe [etsi_ref], 192 Spectrum allocation in Japan [arib_ref]. 194 At present, the SIGFOX LTN radio interface is also compliant with the 195 local regulations of the following countries: Australia, Brazil, 196 Canada, Kenya, Lebanon, Mauritius, Mexico, New Zealand, Oman, Peru, 197 Singapore, South Africa, South Korea, and Thailand. 199 5. Radio Protocol 201 The radio interface is based on Ultra Narrow Band (UNB) 202 communications, which allow an increased transmission range by 203 spending a limited amount of energy at the device. Moreover, UNB 204 allows a large number of devices to coexist in a given cell without 205 significantly increasing the spectrum interference. 207 Both uplink and downlink communications are possible with the UNB 208 solution. Due to spectrum optimizations, different uplink and 209 downlink frames and time synchronization methods are needed. 211 5.1. Uplink 213 5.1.1. Uplink Physical Layer 215 The main radio characteristics of the UNB uplink transmission are: 217 o Channelization mask: 100 Hz (600 Hz in the USA) 219 o Uplink baud rate: 100 baud (600 baud in the USA) 221 o Modulation scheme: DBPSK 223 o Uplink transmission power: compliant with local regulation 225 o Link budget: 155 dB (or better) 227 o Central frequency accuracy: not relevant, provided there is no 228 significant frequency drift within an uplink packet 230 In Europe, the UNB uplink frequency band is limited to 868,00 to 231 868,60 MHz, with a maximum output power of 25 mW and a maximum mean 232 transmission time of 1%. 234 5.1.2. Uplink MAC Layer 236 The format of the uplink frame is the following: 238 +--------+--------+--------+------------------+-------------+-----+ 239 |Preamble| Frame | Dev ID | Payload |Msg Auth Code| FCS | 240 | | Sync | | | | | 241 +--------+--------+--------+------------------+-------------+-----+ 243 Figure 2: Uplink Frame Format 245 The uplink frame is composed of the following fields: 247 o Preamble: 19 bits 249 o Frame sync and header: 29 bits 251 o Device ID: 32 bits 253 o Payload: 0-96 bits 255 o Authentication: 16-40 bits 257 o Frame check sequence: 16 bits (CRC) 259 5.2. Downlink 261 5.2.1. Downlink Physical Layer 263 The main radio characteristics of the UNB downlink transmission are: 265 o Channelization mask: 1.5 kHz 267 o Downlink baud rate: 600 baud 269 o Modulation scheme: GFSK 271 o Downlink transmission power: 500 mW (4W in the USA) 273 o Link budget: 153 dB (or better) 274 o Central frequency accuracy: Centre frequency of downlink 275 transmission are set by the network according to the corresponding 276 uplink transmission. 278 In Europe, the UNB downlink frequency band is limited to 869,40 to 279 869,65 MHz, with a maximum output power of 500 mW with 10% duty 280 cycle. 282 5.2.2. Downlink MAC Layer 284 The format of the downlink frame is the following: 286 +------------+-----+---------+------------------+-------------+-----+ 287 | Preamble |Frame| ECC | Payload |Msg Auth Code| FCS | 288 | |Sync | | | | | 289 +------------+-----+---------+------------------+-------------+-----+ 291 Figure 3: Downlink Frame Format 293 The downlink frame is composed of the following fields: 295 o Preamble: 91 bits 297 o Frame sync and header: 13 bits 299 o Error Correcting Code (ECC): 32 bits 301 o Payload: 0-64 bits 303 o Authentication: 16 bits 305 o Frame check sequence: 8 bits (CRC) 307 5.3. Synchronization between Uplink and Downlink 309 The radio interface is optimized for uplink transmissions, which are 310 asynchronous. Downlink communications are achieved by querying the 311 network for existing data from the device. 313 A device willing to receive downlink messages opens a fixed window 314 for reception after sending an uplink transmission. The delay and 315 duration of this window have fixed values. The LTN network transmits 316 the downlink message for a given device during the reception window. 318 The LTN network selects the BS for transmitting the corresponding 319 downlink message. 321 Uplink and downlink transmissions are unbalanced due to the 322 regulatory constraints on the ISM bands. Under the strictest 323 regulations, the system can allow a maximum of 140 uplink messages 324 and 4 downlink messages per device. These restrictions can be 325 slightly relaxed depending on system conditions and the specific 326 regulatory domain of operation. 328 6. ETSI LTN 330 The ETSI TC EMC and Radio Spectrum Matters (ERM) group has multiple 331 work items dealing with LTN. The objective is to define use cases, 332 system architecture and radio protocols for LTN (or LPWAN), using 333 shared spectrum bands, allowing to offer very low cost subscriptions 334 per device. 336 According to ETSI, LTN is particularly well suited for low throughput 337 machine to machine communication where data volume is limited and low 338 latency is not a strong requirement. Some foreseen applications 339 include remote measurement for agriculture and environment, smart 340 metering for utilities, smart cities applications such as air 341 pollution monitoring or public lighting, etc. 343 LTN could also cooperate with cellular networks to address use cases 344 where redundancy, complementary or alternative connectivity is 345 needed. Low power, very low throughput, very long battery life, 346 simple, effective and robust radio communication principles are the 347 key features of ETSI LTN systems. 349 7. Network Deployment 351 As of today, the SIGFOX LPWAN/LTN has been fully deployed in 6 352 countries, with ongoing deployments on 14 other countries, which in 353 total will reach 316M people. 355 The vast majority of the current applications are sensor-based, 356 requiring solely uplink communications, followed by actuator-based 357 applications, which make use of bidirectional (i.e. uplink and 358 downlink) communications. 360 Similar to other LPWAN/LTN technologies, the sectors that currently 361 benefit from the low-cost, low-maintenance and long battery life are 362 agricultural and environment, public sector (smart cities, education, 363 security, etc.), industry, utilities, retail, home and lifestyle, 364 health and automotive. 366 8. IANA Considerations 368 N/A. 370 9. Security Considerations 372 The radio protocol provides mechanisms to authenticate and ensure 373 integrity of the message. This is achieved by using a unique device 374 ID and a message authentication code, which allow ensuring that the 375 message has been generated and sent by the device with the ID claimed 376 in the message. 378 Security keys are independent for each device. These keys are 379 associated with the device ID and they are pre-provisioned. 380 Application data can be encrypted by the application provider. 382 10. Acknowledgments 384 The authors would like to thank Olivier Peyrusse for the useful 385 inputs and discussions about ETSI LTN. 387 11. Informative References 389 [arib_ref] 390 "ARIB STD-T108 (Version 1.0): 920MHz-Band Telemeter, 391 Telecontrol and data transmission radio equipment.", 392 February 2012. 394 [etsi_ltn] 395 "ETSI Technical Committee on EMC and Radio Spectrum 396 Matters (ERM) TG28 Low Throughput Networks (LTN)", 397 February 2015. 399 [etsi_ref] 400 "ETSI EN 300-220 (Parts 1 and 2): Electromagnetic 401 compatibility and Radio spectrum Matters (ERM); Short 402 Range Devices (SRD); Radio equipment to be used in the 25 403 MHz to 1 000 MHz frequency range with power levels ranging 404 up to 500 mW", May 2016. 406 [fcc_ref] "FCC CFR 47 Part 15.247 Telecommunication Radio Frequency 407 Devices - Operation within the bands 902-928 MHz, 408 2400-2483.5 MHz, and 5725-5850 MHz.", June 2016. 410 Authors' Addresses 412 Juan Carlos Zuniga 413 SIGFOX 414 425 rue Jean Rostand 415 Labege 31670 416 France 418 Email: JuanCarlos.Zuniga@sigfox.com 419 URI: http://www.sigfox.com/ 421 Benoit Ponsard 422 SIGFOX 423 425 rue Jean Rostand 424 Labege 31670 425 France 427 Email: Benoit.Ponsard@sigfox.com 428 URI: http://www.sigfox.com/